1989 Johnson 70 Possible Overcharging & Rectifier/Regulator Replacement

[sumocomputers]

I have a 1989 Johnson 70, and the charging voltage at the cranking battery is about 16.5 volts at idle with just the flushing ears hooked up.

1. I want to connect my cranking battery and my house battery together with a battery switch, and want them both to be able to charge when the engine is running.

2. I also want to make sure that my instruments, fish finder, etc. don't get too high voltage, avoiding damage. Right now I am afraid that 16.5 volts would damage them. Right now we just ghetto-rig them to the house battery, and charge it in the garage with a plug in charger. In other words we have 2 separate battery circuits.

I see that CDI offers a rectifier/regulator part # 193-3408, linked in this post.
http://www.cdielectronics.com/produ...5708-9-17200-9-17200-9-17200-9-17200-9-17200/

My hope is that installing it would bring my charging voltage down to a safe level. My question is if getting the CDI part will accomplish what I want. The CDI instructions still say not to use a maintenance-free battery, and I am not sure if either of my batteries fall into this category. I have included links to both of my batteries below.

I found a thread on continouswave (http://continuouswave.com/ubb/Forum6/HTML/002256.html) where it is suggested to use a couple of later model BRP official rectifiers (one air cooled, the other water cooled), but I am not sure if this is preferable to something like the CDI. The CDI is certainly cheaper, and is supposed to be a match. The BRP seems like tribal knowledge.

I have the official service manual, and it tells you how to check the rectifier, but I don't see anything in there that tells me what the voltage should actually be when engine is running, and the specifications for the battery type are sort of generic. Again, my main concern is damaging things like fish finder, etc.

Any help is appreciated.

Thanks,

Chris

Here is a photo of the cranking battery I have:
https://www.dropbox.com/s/mbpejp3ltdsg22e/2015-02-23 15.00.19.jpg


Here is the house battery I have:
https://www.dropbox.com/s/4ybxrqwyje1i1aw/2015-02-23 15.01.24.jpg

 

[F_R]

Go with the CDI regulated rectifier. That is what it is made for (eliminating overcharging). It is totally normal for the original unregulated system to go to 16 volts, or even a bit more.

 

[sumocomputers]

Thanks; easy enough to address overcharging the batteries themselves.

Any need to be concerned about electronics like fish finder handling 16+ volts, or will the CDI drop it down? That is the main question that I can't seem to find an answer to on the CDI website.

 

[emdsapmgr]

These modern electronic devices are made to handle unusual marine type fluctuations. If the voltage is too low, they shut off. The usually tolerate higher voltages better. 16.5 unregulated volts is "normal" for that engine when running on plane with charged up batteries. Maybe a little high at idle. If it does not go much higher-it should be ok as is.

 

[sumocomputers]

Sweet guys, thanks for the advice. I will have to consider if it is worth paying $80+ on the regulator, but it seems my batteries and electronics should be OK without it.

 

[Vic.S]

Not perhaps the best idea to connect both batteries together

Proper battery selector switch possibly better. Then you can recharge the cranking battery then switch over to the house battery to power everything until you next need to start the engine. Or just use the individual isolator switches to do the same thing.

Perhaps better still use a VSR to control the charging without the need for manual selection. Use a large dual purpose battery for everything including engine starting but charge a small reserve battery, that can be used if/when necessary, via the VSR. See Nigel Calder's book for details.

Alternatively use a diode splitter. Normally the objection is the volts drop ( around 0.7 volts) across diodes but in view of the high voltage from the unregulated rectifier it might just be a good option . It will automatically charge both batteries simultaneously while keeping them isolated from each other and will drop the voltage a little.

A VSR or a diode splitter avoid the possible trouble that will result if both batteries are switched out while the engine is running using manual switching.

I notice BTW that your cranking battery is a larger capacity than your house battery. Unusual with a two battery system! Two the same size perhaps but more normal for the house battery to be larger than the cranking battery. Unless you need very little in the way of power for a few small instruments of course..

 

[joetheis]

Before I dive into my wallet and start to modify, I'd take a multi meter at the battery and check the actual voltage going into the battery, at idle and say 2500 rpm.
On my buddies boat, he thought there was something wrong with his Honda 90, as it read a smudge above 12 volts. Replaced all the charging parts, only to find out his gauge was reading low!
On my bikes, I run my gps and radio through the headlight circuit to prevent over voltage.
In a boat, hmmmmm, but you get the idea, draw some voltage off.
Joe
As always take any advice I give with a can of beer er 2

 

[sumocomputers]

Hey guys, thanks for the additional info, and I will look at a VSR. And my idea was to use a battery switch like the Blue Sea or Perko.

But I also got a response from CDI regarding their rectifier/regulator, and they said that both of my batteries are maintenance-free, which I guess is not recommended, apparently with or without the CDI unit, and they recommend replacing both of them with something from Interstate/Exide, which is both a starting and deep cycle. Sadly, I need to educate myself on batteries, as I just don't know what to make of that.

And as for what I run for accessories/gauges: Sierra Analog Temp Sensor, small Lowrence HD 4, Running Lights, Horn, so not much probably.

Any thoughts on my particular batteries? These are what came with the boat/motor, so I realize the guy before me may have bought the wrong thing. If I should replace one or both, I am willing to do that.

 

[F_R]

Well, you asked for thoughts, so here goes: In the first place I don't know why you figure you need two batteries, but if that is your wish so be it. In the second place, I think it is possible to be too educated. I may not be the sharpest tack in the box, but the plain ol' off-the-shelf Wal Mart battery in my boat has been in there 6 years and sadly neglected. When it goes, it is time, and I'm sure I'll probably go back to Wal Mart. I sure wouldn't replace it just because it is the "wrong type". Hey, if it is good enough for a Lexus, it is good enough for my little tin boat. And yes it runs up over 16 volts.

 

[sumocomputers]

Well, I don't know that I need 2 batteries, but the boat came with 2. I just figured if I were out for long periods of time, I could run all the electronics from the 2nd one, always making sure my starting battery was full.

I am actually not that concerned with killing my batteries, but more on the electronics, which really means the Lowrence. I just now tracked down the manual, and it can take from 10-17 volts, so at this point, I think I am going to scale back my plan, and just run with what I have, and see what happens. If I kill these batteries, I can always look at getting something different.

 

[Fed]

How did you measure the 16.5 Volts?

 

[F_R]

I would have to assume that anybody making marine electronics (including Lowrence) would know that the majority of outboard motors have unregulated charging systems and provide an internal regulator in their product. If they don't, shame on them.

BTW, I fully understand the reasoning behind wanting a spare starting battery "just in case". But I'm sure you also realize the motor can be rope started in an emergency. If you doubt your ability to do that, try it sometime. I'm far from being the Impossible Hulk, but I've rope started motors a lot bigger than that one.

 

[gm280]

I won't worry too much about the voltages going to any new electronics these days. Most everything has voltage regulation in their circuits and can easily handle higher voltages. Most any off the shelf regulators can handle up to +37 volts before there is any issue. So that shouldn't be much of a concern. However, if your battery actually reads 16.5 volts even at idle, you have one serious alternator to drive that high a voltage level at the battery. And if you do, post those readings back on here and let us know. Your battery should drop that high a voltage down pretty well... The battery acts like both a storage source and a filter to make spicks and such smooth out to a lower reading. While the battery certainly won't regulate itself, it does smooth some spicks and changes in the voltage coming from the alternator. That's why open circuit voltages from the alternators are usually higher then when connected up to the battery. JMHO!

 

[sumocomputers]

So the way I checked the voltage was this:

Engine leads hooked up to starting battery, and nothing else.
Started the engine at low idle with flushing ears.
Put my Fluke 73 on the terminals and got about 16.5 volts for several minutes.

 

[Fed]

Pretty convincing, I have to say I didn't think they would put out that at idle RPM.
I did read recently that a fully charged battery has an internal resistance around 9 meg-ohms so for all purposes it's like having no battery there at all.
I've seen close to 18 Volts at WOT on a full battery.
Check your batteries carefully to see if they have any sneaky lift off lids that give access to the filler holes, mine has.

 

[Danielcan]

As I understand it, the suggestion for a lead acid battery over a sealed, maintance free glass mat or gell cell is that--- in the event your rectifier overcharges your battery the electrolyte (acid) will evaporate, this can be replaced on a wet cell (lead acid) battery by adding distilled water. A sealed battery will vent the gas Presure, but it can't be added back, and your out one expensive battery.

My question is, will a regulated rectifier keep charging my battery even when it's full? If so how can I protect my battery from over charging?

 

[Big Fish Billy]

A fully charged battery is 12.63 volts, so before starting the engine, if it reads 12, it's already below fully charged. If while running, it doesn't rise to 13.4 at idle and goes over 14.7 at half throttle or above, the rec/reg isn't working properly...from your first post, yours sounded fine. Batteries boil out if you're consistently blasting 16 volts in there. (but buying a battery for $75 is cheaper than a rec for a few hundred, your choice there) My Hummingbird shows the voltage, and alarms at 16v and shuts down. A previous poster mentioned a Perko switch with 1,2 or Both. As recommended, keep 1 for starting, switch to 2 while fishing (not running), and Both while running home. If you're starting out with a fully charged battery, you won't see as much charging voltage as a discharged battery, but it will always be in the 13v range. Hope it helps. When I had my Force 40, over charging at 16v, my battery lasted about 5 years, my music radio and courtesy lights didn't.

 

[Crosbyman]

• Model: 7812
• Catalog #: 2761771

RadioShack? +12V Fixed-Voltage Regulator 7812 $1.99

http://www.radioshack.com/radioshack...2/2761771.html $1.99

3-4 of these wired in parallel and mounted on a small aluminum plate will get you **** flat 12volts from anything between 12-35 vdc input
each chip handles 1 amp current

Great for sensitive intruments like depth-fish finders

other types available if you Google but these are dirt cheap and easy to hook-up

 

[Big Fish Billy]

Nice...we'll have to try to grab a few before Radio Shack finishes going out of business....

 

[Fed]

My question is, will a regulated rectifier keep charging my battery even when it's full? If so how can I protect my battery from over charging?

Your regulator will keep the voltage below 15V and that won't cook your battery.